linux-kernel - Re: [RFC 00/29] De-stage android's sync framework

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Date:	Tue, 19 Jan 2016 15:52:26 -0200
From:	Gustavo Padovan <gustavo@...ovan.org>
To:	John Harrison <John.C.Harrison@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	dri-devel@...ts.freedesktop.org, daniels@...labora.com,
	Arve Hjønnevåg <arve@...roid.com>,
	Riley Andrews <riandrews@...roid.com>,
	Rob Clark <robdclark@...il.com>,
	Greg Hackmann <ghackmann@...gle.com>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Subject: Re: [RFC 00/29] De-stage android's sync framework

2016-01-19 John Harrison <John.C.Harrison@...el.com>:

> On 19/01/2016 15:23, Gustavo Padovan wrote:
> >Hi Daniel,
> >
> >2016-01-19 Daniel Vetter <daniel@...ll.ch>:
> >
> >>On Fri, Jan 15, 2016 at 12:55:10PM -0200, Gustavo Padovan wrote:
> >>>From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> >>>
> >>>This patch series de-stage the sync framework, and in order to accomplish that
> >>>a bunch of cleanups/improvements on the sync and fence were made.
> >>>
> >>>The sync framework contained some abstractions around struct fence and those
> >>>were removed in the de-staging process among other changes:
> >>>
> >>>Userspace visible changes
> >>>-------------------------
> >>>
> >>>  * The sw_sync file was moved from /dev/sw_sync to <debugfs>/sync/sw_sync. No
> >>>  other change.
> >>>
> >>>Kernel API changes
> >>>------------------
> >>>
> >>>  * struct sync_timeline is now struct fence_timeline
> >>>  * sync_timeline_ops is now fence_timeline_ops and they now carry struct
> >>>  fence as parameter instead of struct sync_pt
> >>>  * a .cleanup() fence op was added to allow sync_fence to run a cleanup when
> >>>  the fence_timeline is destroyed
> >>>  * added fence_add_used_data() to pass a private point to struct fence. This
> >>>  pointer is sent back on the .cleanup op.
> >>>  * The sync timeline function were moved to be fence_timeline functions:
> >>>	 - sync_timeline_create()	-> fence_timeline_create()
> >>>	 - sync_timeline_get()		-> fence_timeline_get()
> >>>	 - sync_timeline_put()		-> fence_timeline_put()
> >>>	 - sync_timeline_destroy()	-> fence_timeline_destroy()
> >>>	 - sync_timeline_signal()	-> fence_timeline_signal()
> >>>
> >>>   * sync_pt_create() was replaced be fence_create_on_timeline()
> >>>
> >>>Internal changes
> >>>----------------
> >>>
> >>>  * fence_timeline_ops was removed in favor of direct use fence_ops
> >>>  * fence default functions were created for fence_ops
> >>>  * removed structs sync_pt, sw_sync_timeline and sw_sync_pt
> >>Bunch of fairly random comments all over:
> >>
> >>- include/uapi/linux/sw_sync.h imo should be dropped, it's just a private
> >>   debugfs interface between fence fds and the testsuite. Since the plan is
> >>   to have the testcases integrated into the kernel tree too we don't need
> >>   a public header.
> >>
> >>- similar for include/linux/sw_sync.h Imo that should all be moved into
> >>   sync_debug.c. Same for sw_sync.c, that should all land in sync_debug
> >>   imo, and made optional with a Kconfig option. At least we should reuse
> >>   CONFIG_DEBUGFS.
> >These two items sounds reasonable to me.
> 
> I have just posted our in-progress IGT for testing i915 syncs (with a CC of
> Gustavo). It uses the sw_sync mechanisms. Can you take a quick look and see
> if it is the kind of thing you would expect us to be doing? Or is it using
> interfaces that you are planning to remove and/or make kernel only?
> 
> I'm not sure having a kernel only test is the best way to go. Having user
> land tests like IGT would be much more versatile.

I agree with you, we should allow IGT and other test tools to access
sw_sync. include/linux/sw_sync.h can be kept private, but the uapi one
needs wil be needed for testing, unless we replicate the header file
inside IGT, but not sure if it is a good idea.

	Gustavo